There are many variables that determine how long recovery takes and what its path looks like.
I'm aware there are some statistics out there (and I have read one that directly mentions "7 years"), and they may be useful in some situations.
I wouldn't let myself become invested in any specific length of time, Palmtreechick. To do so will most likely be misleading for you and could feel overwhelming, and/or put pressure on you.
It is statistically accurate that the longer someone suffers from an eating disorder, the longer it takes and the more challenging it is to recover. However, this does not always hold true.
Some other factors that affect treatment and recovery time are: what someone means by "recovery;" how medically serious the ED is/has been; how intense the symptoms are (to what extent someone uses the ED behaviors- which is an indicator of how dependent he/she is upon the disorder); what kind of support someone has from family, friends, a community; to what extent someone can develop interests beyond the disorder (can he/she become invested in life to a degree that those interests becomes strong enough for the person to have the courage to change the relationship with the ED); and, not least, is someone willing to take a chance, to not know what may happen, but to try something different- something different than the familiarity of the eating disorder.
There are other factors, as well as variations of these listed above. You can see that myriad things affect the treatment and recovery process. I vote for continuing to pay attention to what is right before us, right now, that we can do for ourselves. You know me... I vote for staying in the present, where we have power, instead of getting lost out in the future, where all we can do is worry about what might or might not happen.
Oh, speaking of power, Super Egg asked an interesting question about power a day ago. I'll write an answer later today or tomorrow for that comment.